The present invention relates to a catalyst suitable for dehydrocoupling of toluene or xylene, and a process for dehydrocoupling of toluene or xylene in the presence of the catalyst.
Processes for synthesizing 1,2-diphenylethane or 1,2-diphenylethylene and these derivatives by dehydrogenation of toluene or xylene have been numerously known hitherto. For instance, processes of these dehydrogenation which utilize halogen, sulfur, carbon disulfide and the like as the hydrogen acceptor have been known for a long time, however, there are several inconveniences in these processes such as the high cost of the hydrogen acceptor, the formation of corrosive substances and the contamination of the product by halides and sulfides.
As a process in which the inconveniences in the dehydrogenation have been raveled out, a process of using oxygen as the hydrogen acceptor has been proposed, and the possible use of a metal oxide such as lead oxide as the oxygen source for the hydrogen acceptor has been disclosed in U.S. Pat. No. 3,963,793. Namely, in the disclosed process, propene, toluene, acetic acid and other compounds can be converted into the respective dehydrocoupled compounds in the presence of "a reagent which contains oxygen and can be regenerated" and in the absence of free molecular oxygen. "The reagent which contains oxygen and can be regenerated" mentioned herein is a specified metal oxide, and in U.S. Pat. No. 3,963,793, thallium trioxide is disclosed other than bismuth trioxide. Many proposals have been given for dimerization using such a metal oxide as the catalyst, and it has been known that various metal oxides are respectively effective as a catalyst in dimerization.
In addition, as the metal oxide, lead oxide, thallium oxide, bismuth oxide and other oxides have been known as in U.S. Pat. No. 4,243,825, however, the effectiveness of these oxides themselves is not so remarkable as the catalyst in dimerization.
Accordingly, in U.S. Pat. No. 3,963,793, a method in which thallium oxide or bismuth oxide is carried on a basic carrier of a specific surface area of higher than 20 m.sup.2 /g in order to raise the catalytic activity of each oxide is disclosed.
The object of the present invention is to provide a catalyst which is useful to the dehydrocoupling of toluene or xylene into 1,2-diphenylethane and 1,2-diphenylethylene or 1,2-ditolylethane and 1,2-ditolylethylene in an improved yield, and is to provide a process for profitably dehydrocoupling toluene or xylene by the use of the catalyst provided by the present invention.